Broadnose sevengill shark

The broadnose sevengill shark (Notorynchus cepedianus) is the only extant member of the genus Notorynchus, in the family Hexanchidae. It is recognizable because of its seven gill slits, while most shark species have five gill slits, with the exception of the members of the order Hexanchiformes and the sixgill sawshark. This shark has a large, thick body, with a broad head and blunt snout. The top jaw has jagged, cusped teeth and the bottom jaw has comb-shaped teeth. Its single dorsal fin is set far back along the spine towards the caudal fin, and is behind the pelvic fins. In this shark the upper caudal fin is much longer than the lower, and is slightly notched near the tip. Like many sharks, this sevengill is counter-shaded. Its dorsal surface is silver-gray to brown in order to blend with the dark water and substrate when viewed from above. In counter to this, its ventral surface is very pale, blending with the sunlit water when viewed from below. The body and fins are covered in a scattering of small black & white spots. In juveniles, their fins often have white margins. It is also known as sevengill shark or simply sevengill and was formerly known as cow shark and mud shark; it is called sevengill due to its seven gill slits. Because of this, it was listed along with the sharpnose sevengill shark (Heptranchias perlo) by Guinness World Records as having the most gill slits. It is similar to the sharpnose sevengill shark but the latter has a pointed snout and lacks spots on its dorsal surface. The sevengill species are also related to ancient sharks as fossils from the Jurassic Period (200 to 145 million years ago) also had seven gills. As recently as the 1930s and 1940s, the shark was targeted by fisheries along the coast of California and, once the commercial fishery receded, recreational fishing of the shark started in the 1980s and 1990s. This species has recently (since 2019) been targeted by Orcas in False Bay on the South African coast. The length at birth is 40–45 cm (15.5–17.5 in) while the mature male length is 1.5 m (4.9 ft) and mature female length is around 2.2 m (7.2 ft). The maximum length found is 3 metres (9.8 ft). The shark is large and active and has a large head but small eyes and snout. The shark has one dorsal fin at the back of the body that spans from the insertion to the tops of the pelvic fins. The broadnose sevengill shark is also known as sevengill shark or simply sevengill and was formerly known as cow shark and mud shark; it is called sevengill due to its seven gill slits. Because of this, it was listed along with the sharpnose sevengill shark by Guinness World Records as having the most gill slits. It is similar to the sharpnose sevengill shark but the latter has a pointed snout and lacks spots on its dorsal surface. The sevengill species are also related to ancient sharks as fossils from the Jurassic Period (200 to 145 million years ago) also had seven gills. The broadnose sevengill has so far been found in the western Pacific Ocean off China, Japan, Australia, New Zealand, the eastern Pacific Ocean off Canada, United States and Chile, and the southern Atlantic Ocean off Argentina and South Africa. In San Francisco, California, it is significantly found in the San Francisco Bay particularly near the Golden Gate Bridge and Alcatraz Island. Large, old individuals tend to live in deep offshore environments as far down as 446 feet (136 m). However, most individuals live in either the deep channels of bays, or in the shallower waters of continental shelves and estuaries. These sharks are mainly benthic in nature, cruising along the sea floor and making an occasional foray to the surface. Other foreign names are cação-bruxa (Portuguese), cañabota gata (Spanish), ebisuzame (Japanese), gatita (Spanish), gevlekte zevenkieuwshaai (Dutch), kammzähner (German), koeihaai (Afrikaans), k'wet'thenéchte (Salish), minami-ebisuzame (Japanese), platneus-sewekiefhaai (Afrikaans), platnez (French), requin malais (French), Siebenkiemiger Pazifischer Kammzähner (German), siedmioszpar plamisty (Polish), tiburón manchado, tiburón de 7 gallas, tiburón pinto and tollo fume (all Spanish), and tuatini (Maori). An opportunistic predator, the broadnose sevengill preys on a great variety of animals and has been found at a depth of 1,870 feet (570 meters) in offshore waters. It has been found to feed on sharks (including gummy shark, one of its main prey, and cowsharks), rays, chimaeras, cetaceans, pinnipeds, bony fishes and carrion and will also feed on whatever it finds such as shark egg cases, sea snails and remains of rats and humans. Research in 2003 found that its diet consisted of 30% mammals with a frequency of occurrence of 35%. It is a frequent top predator in shallow waters and has comb-like teeth, with the upper teeth having slender, smooth edged cusps to swallow small enough prey whole and lower teeth broad enough to bite prey to pieces. These sharks occasionally hunt in packs to take down larger prey, using tactics such as stealth to succeed. After feeding, it slowly digests the food for several hours and days and can go weeks until eating again. Large predatory sharks such as the great white shark can be a threat and cannibalism among this shark has also been recorded. When not highly active, it hunts stealthily while making very little movement except for moving its caudal fin until dashing to strike. It can be one of the most abundant predators in coastal waters in summer and, in southeast Tasmania, there is a high abundance of elasmobranches including the gummy shark in coastal regions in summer. In New Zealand, it is also one of the most common inshore sharks. While it is mainly a nocturnal forager, it may opportunistically feed on prey casually found during the day, however, research in 2010, found even amounts of activity during day and night. During this research, this shark was consistently detected at all depths from bottom to near surface whereas it was the substrate during the day. It also found that as Norfolk Bay does not have adequate shelter cover, this species may use group formation to avoid predation.